1. Field of the Invention
The present invention relates to a multi-unit air conditioner connected with a compressor and at least two indoor heat-exchangers.
2. Description of the Prior Art
Generally, an air conditioner comprises a compressor, an indoor heat-exchanger, a capillary tube, and an outdoor heat-exchanger, for adjusting indoor air conditions to an optimum state by means of refrigerant circulating therethrough.
Recently, a multi-unit air conditioner is available. The multi-unit air conditioner is so-called because it includes a plurality of indoor heat-exchangers respectively connected to each other in parallel and those heat-exchangers are connected to a high-capacity compressor in series. Indoor heat-exchangers of the multi-unit air conditioner are installed at respective room areas.
An example of such a multi-unit air conditioner is shown in FIG. 1.
As shown in the figure, the multi-unit air conditioner includes two compressors and 12, one outdoor heat-exchanger 20, and three indoor heat-exchangers 51, 52a, and 52b.
The outdoor heat-exchanger 20 includes a circulation path 21 through which the refrigerant compressed in the compressor 11 is circulated, and two circulation paths 22a, 22b through which respective portions of the refrigerant compressed in the compressor 12 are circulated. Outlets of the two paths 22a, 22b converge at 22c.
An outlet of the circulation path 21 is connected with the single-unit indoor heat-exchanger 51 through a refrigerant pipe 1. A capillary tube 31 for reducing the pressure of the refrigerant passing therethrough is installed in the refrigerant pipe 1 between the circulation path 21 and the single-unit indoor heat-exchanger 51.
Another refrigerant pipe 2 connected with the multi-unit circulation path 22 is divided into two branches respectively connected with multi-unit indoor heat-exchangers 52a and 52b.
A capillary tube 33 is installed in the refrigerant pipe 2 upstream of the point where the latter is divided into two branches 2a, 2b, for reducing the pressure of the refrigerant. A flow controlling pipe 3 provided with a flow controlling valve 43 is connected with the capillary tube 33 in parallel. When the valve 43 is open, refrigerant flows therethrough and by-passes the capillary tube 33.
The branches 2a and 2b are provided with capillary tubes 32a and 32b, respectively, and a pair of opening/closing valves 42a and 42b are connected to respective ones of the capillary tubes 32a and 32b in series.
An outlet of the single-unit indoor heat-exchanger 51 is connected with an inlet of the single-unit compressor 11, and the outlets of both of the multi-unit indoor heat-exchangers 52a and 52b are connected with an inlet of the multi-unit compressor 12.
In the multi-unit air conditioner constructed as above, a first supply of refrigerant is circulated through a single-unit refrigerant circulating cycle, i.e., the refrigerant compressed in the single-unit compressor 11 is circulated subsequently through the single-unit circulation path 21 of the outdoor heat-exchanger 20, the capillary tube 31, the single-unit indoor heat-exchanger 51, and back to the single-unit compressor 11.
A second supply of refrigerant compressed in the multi-unit compressor 12 is circulated through a multi-unit refrigerant circulating cycle, i.e., the refrigerant compressed in the multi-unit compressor 12 is subsequently circulated through the multi-unit circulation path 22 of the outdoor heat-exchanger 20, capillary tubes 32 and 33, multi-unit indoor heat-exchangers 52a and 52b, and back to the multi-unit compressor 12.
Operations of the single-unit and multi-unit refrigerant circulating cycles are respectively controlled.
More specifically, when both of the multi-unit indoor heat-exchangers 52a and 52b are simultaneously in use, the flow controlling valve 43 is in a closed state, while both of the opening/closing valves 42a and 42b are in an open state.
The flow controlling valve 43 is opened and one 42a of the opening/closing valves 42a and 42b is closed, when only one (e.g., 52b) of the multi-unit indoor heat-exchangers 52a and 52b is in use. At this instance, the refrigerant flows through the flow controlling valve 43 so that it does not flow through the capillary tube 33. Thereby, a moderate amount of refrigerant for efficient compressing can be converged back into the multi-unit compressor 12 solely from indoor heat-exchanger 52b.
However, the conventional multi-unit air conditioner has drawbacks as explained below.
When only one (e.g., 52b) of the indoor heat-exchangers 52a and 52b is operated, the moderate amount of the refrigerant for compressing is returned to the multi-unit compressor 12 since the flow controlling valve 43 is opened. At the same time, however, the opening of the valve 43 causes the amount of refrigerant supplied into the one indoor heat-exchanger 52b in use to be increased. Accordingly, some of that refrigerant supplied into the indoor heat-exchanger 52b is incompletely evaporated, and supplied into the compressor 12 in a liquid state which causes a malfunction of the compressor 12. In addition, an excessive amount of refrigerant supplied into the indoor heat-exchanger 52b can cause a freezing of the evaporator while it is being evaporated therein.